The objectives of this proposed research are: 1) to characterize the Mexican-American population of Bexar County, Texas with respect to an array of discrete, polymorphic gene loci, and to estimate the level of Amerindian admixture to the population; 2) to test the hypothesis that the elevated prevalence of diabetes and diabetes related cardiovascular risk factors in Mexican-Americans is due to the presence of predisposing genes derived from the Amerindian gene pool; 3) gene frequencies at 25 polymorphic gene loci will be used to test for between group heterogeneity in subgroups of the Mexican-American population to determine whether between group differences with respect to diabetes are solely due to environmental factors, or whether a more complex gene-environment model is necessary to explain these differences.